Single-cell mechanical flotation system

ABSTRACT

A mechanical flotation system having only one cell may be nearly as efficient as one having two or more cells, yet provide an apparatus with a considerably smaller footprint, significantly reduced capital and operating costs, as well as be resistant to floating oil recovery platform wave effects. The single-cell mechanical flotation system may have one skim collection channel that at least partially surrounds a single gas ingestion and mixing mechanism. At least one baffle may direct suspended matter or floc toward the skim collection which may be circular. The gas layer over the liquid is not vented for the purpose of gasification. The vessel may be a cylindrical pressure vessel oriented vertically, and optionally the inlet may be tangential to the periphery of the vessel to impart liquid rotation inside the vessel when liquid is introduced.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for removingsuspended matter from a liquid in general and for removing oil and othersuspended particulate contaminants from the water stream in the oilfield in particular, and in one non-limiting embodiment, the inventionrelates to removing suspended matter from a liquid on offshore platformswhere small footprint of processing apparatus is of important economicaladvantage both in capital and operating expenditure.

BACKGROUND OF THE INVENTION

Gas flotation is one of the most efficient and widely accepted methodsused in variety of industries where removal of solid or immiscibleliquid phases is of interest. In particular, in the petroleum industry,the ever-increasing volume of associated water produced from thehydrocarbon reservoirs as a side product has become a major issue to beaddressed by the producers. Environmental awareness and regulations areincreasingly challenging the producers to achieve a high degree ofpurification in the treated water streams prior to discharge orre-injection. Gas flotation has proven one of the most efficient andeconomical polishing processes compared to other methods and availabletechnologies. Simultaneously, the economical penalty for additionalwater treatment capacity and footprint of apparatus are major factors inbudgeting and decision making for the producers.

Previous endeavors include apparatus with at least two active capacitiesor gasification chambers with a common skimmer at the center of ahorizontal tank, such as those taught in U.S. Pat. Nos. 4,990,246 and5,348,648. Gasification is applied by means of at least two rotorassemblies located at the center of each gasification chamber. Thecommon skimmer consists of a movable part having a downwardly openingannulus extending around a fixed part. The floating skimmer assemblymust be of an exact weight, hence multiple adjustments by means ofadding and removing of counterweights to the assembly is required. Theassembly must be designed to specific needs of each application and mustbe adjusted for any variations to the froth rate, feed rate and othervariables. This vulnerability to process variations is a major concernto the operation of these systems in continuous operation as constantmonitoring and maintenance is required due to the unpredictable natureof production operation.

Another known flotation apparatus is disclosed in the U.S. Pat. No.5,080,780 for a vertical single chamber unit. The system includes avertical tank with inlet and outlet connections. The feed enters thetank from the bottom through an inlet distributor and moves upwardly andover a circular baffle arrangement to the outlet chamber. A separategasification system is installed on the outside of the tank, includinggas and liquid transfer lines, at least one pump and one vacuum pump.The pump suction is flooded by the treated liquid leaving the tank. Thisliquid is discharged from the pump and into the vacuum pump at specificrate and pressure dictated by the vacuum pump design. The vaporconnection of the vacuum pump is piped to the top portion of the tankwhere the overhead vapors are drawn into the vacuum pump and mix withthe motive fluid. This mixture is then released into the tank from thebottom and gas bubbles generated in this recycle line provide theflotation effect within the tank. Even though practical, this systemsuffers from inefficient distribution of gas, reduced capacity due to anadditional recycle stream and additional space and attention requiredfor the auxiliary gasification system.

U.S. Patent Application No. 2003/0213735 A1 to Stacy, et al. describesan improved design for a gas flotation apparatus with rotors as themeans for gasification. The apparatus includes two gasificationchambers, each equipped with a dedicated rotor assembly, a commonskimming trough in the middle of the horizontal tank and a thirddischarge compartment. This apparatus has a smaller footprint and lowerpower consumption for treatment of produced water due to a reducednumber of gasification chambers and rotor assemblies from a typicalfour-cell unit and maintains relatively high contaminant removalefficiency. Froth can be collected in multiple locations in eachchamber. The primary means of skim collection is the common reservoirintegral with a partition between the two gasification chambers. Treatedliquid leaves the second gasification chamber through a control valveand into the discharge chamber where additional skimming and levelcontrol mechanisms are required for final discharge of the treatedliquid.

Even though these discussed systems offer improvements to thetraditional mechanical or hydraulic gasification and have proven viablealternatives to such units, where a smaller footprint is desired such ason an offshore platform where space is at a premium, there still remainproblems and areas of improvement driven by economic and performancecriteria.

It would be desirable if an apparatus could be devised to overcome someof the problems in the conventional systems for removing suspendedmatter from a liquid, particularly in systems used on floating offshorehydrocarbon recovery platforms where the action of the waves upon theapparatus tends to cause the suspended matter to contaminate therecovered water. Further, it would be additionally desirable to reducethe footprint of separation systems for even stationary offshoreplatforms.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anapparatus for removing suspended matter from a liquid, which apparatusis particularly suited to be used on floating and stationary offshorehydrocarbon recovery platforms.

It is another object of the present invention to provide a single-cell,mechanical, cylindrical gas flotation system having a reduced footprint,reduced power requirements and reduced capital and operating costs thatovercomes the adverse wave effects on floating platforms.

In carrying out these and other objects of the invention, in onenon-limiting embodiment, there is provided an improved apparatus forseparating an immiscible phase from another liquid phase by means ofcreating an abundance of gas bubbles by rotor action in the liquid, andbringing the bubbles in contact with immiscible contaminants, whether insolid or liquid state, and removing the contaminants by promotingattachment of bubbles and contaminants, thus increasing the buoyancy ofthe resulting floc and floating the floc to the interface to form afroth and removing the froth by means of hydraulic drainage to acollection reservoir.

In a refined, non-restrictive embodiment, there is provided a holdingtank that contains only one gasification chamber, hence significantlyreducing the size, weight and power consumption of the apparatuscompared to prior devices. In another non-limiting refinement, the selfinduction mechanism of internal gas circulation may be preferredcompared to external recycle vacuum pump systems with complicated pumpand piping assemblies or external gas sources which require continuousgas consumption and purge from the apparatus. In another non-restrictiveversion, the operating pressure of the apparatus may be adjusted toprocess requirements, as contrasted with external recycle vacuum pumpswhich are limited to a specific discharge pressure by design. In anothernon-limiting refinement, a single cell unit with a self-inducedmechanical rotor has proven much more efficient as compared with otheravailable single-cell flotation technologies utilizing external vacuumpumps, sparging gas systems and all variations thereof. In anothernon-restrictive embodiment, the design of the current apparatus hasbenefited from an abundance of field trial data and reliable and proventheoretical methodology developed for it.

In a different, non-limiting form there is provided an apparatus forremoving suspended matter from a liquid where the apparatus includes avessel for receiving a flow of liquid having suspended matter therein,an inlet to introduce the flow of liquid into the vessel, and an outletfor removing clarified liquid from the vessel. There is also included agas layer in the upper portion of the vessel and a mechanism (e.g. rotorassembly) in the vessel for ingesting and mixing gas into the liquid ofthe vessel for creating a turbulent area and for attracting thesuspended matter and for carrying the suspended matter to an upperportion of the vessel, where the interface of the gas layer and liquidis a liquid level. There is additionally included a skim collectionchannel at least partially surrounding the mechanism for collectingsuspended matter in the upper portion of the vessel and removing thesuspended matter by a drain. In another non-restrictive embodiment theinvention concerns methods of using apparatus of this type.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, cross-sectional illustration of one embodiment ofthe single-cell mechanical flotation system of the invention where thevessel is oriented horizontally;

FIG. 2 is a schematic, cross-sectional illustration of anotherembodiment of the single-cell mechanical flotation system herein wherethe vessel is oriented vertically;

FIG. 3A is a schematic, top view of a circular skim collection channel;

FIG. 3B is a schematic, side view of the circular skim collectionchannel of FIG. 3A;

FIG. 4A is a schematic, top view of an alternate, circular skimcollection channel;

FIG. 4B is a schematic, side view of the circular skim collectionchannel of FIG. 4A; and

FIG. 4C is an alternate, schematic, side view of the circular skimcollection channel of FIG. 4A.

It will be appreciated that the Figures are schematic illustrations thatare not necessarily to scale or proportion in part to further illustratethe important parts of the invention.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that an efficient apparatus for removingsuspended matter from a liquid may have only one gasification chamber,i.e. one chamber for mixing a gas with the liquid to separate suspendedmatter therefrom. In one non-limiting embodiment, the influent may bewater contaminated with oil and other suspended particulates. It is tobe understood that the present invention has utility in numerousapplications in which it is desirable to separate suspended matterand/or oil from a liquid, and that the suspended matter, the liquid, orboth may be the desired product of the process. Thus, although theinvention is described herein in terms of removing oil and oily solidsfrom water, the apparatus and methods may be applied to otherliquid/suspended matter separation processes.

It will be appreciated that throughout the specification and claims,reference to the singular includes the plural, and reference to theplural includes the singular, unless expressly noted otherwise.Referring to FIG. 1, the present apparatus or system 10 consists of acylindrical vessel 12 capable of withholding high internal pressure,with at least one inlet 14 and at least one outlet 16 to accommodate theflow of contaminated liquid 18 into the apparatus 10 and flow of treatedeffluent out of the apparatus 10, respectively. In one non-limitingembodiment vessel 12 has a continuous cylindrical sidewall and iscapable of withstanding substantial internal pressures as may beencountered when processing produced water from an oil well. The vessel12, is entirely or at least partly utilized to bring into contact theincoming liquid 18 with small gas bubbles 20 generated by a rotatingaction of a rotor or depurator or other mixing device 22, submerged inthe liquid 18. Gas ingesting and mixing mechanisms 22, in onenon-limiting embodiment, are preferably the devices of U.S. Pat. No.3,993,563, incorporated by reference herein, although it will beappreciated that other devices, including but not limited to, simpleaerators, may be used. The rotor assembly 22 in one non-limitingembodiment as a minimum can comprise a stand pipe, disperser 23, hood,rotor and a vertical shaft connected to a motor drive assembly.

The purpose of the rotor assembly 22 is to induce gas from a gas layerin the upper or top portion 24 of the vessel 12 into the liquid. The gasis circulated from the vapor or gas area of the vessel 12 into theliquid 18 through a single or a plurality of openings or draft tubes 26.In doing so, the volume of the gas in circulation is dispersed intoplurality of bubbles 20 which create a large surface area by rotor 22action. The gas bubbles 20 travel towards the interface 28 due to theirbuoyancy and provide the opportunity of contact with the suspendedcontaminant in the liquid 18. These contaminants then will be carriedwith the gas bubbles 20 to the surface 28, where they form adistinguishable thin layer at the surface of the liquid 18. The gas,after breaking through the liquid surface, then returns to the vaporportion of the vessel 12 and continues to recycle within the capacity ofthe vessel 12, without being consumed.

In one non-restrictive embodiment, the vessel 12 can be ahorizontally-oriented cylinder, with an inlet chamber 32, gasificationchamber 30 and outlet chamber 54 as specifically exemplified in FIG. 1.The contaminated liquid enters the tank into the inlet chamber 32. Inthis embodiment, the capacity of inlet chamber 32 allows for partialseparation of larger contaminants and liquid continues to flow downwardunder the partition 34 into gasification chamber 30. The capacity withinthe gasification chamber 30 is mixed with the induced gas in a multitudeof passes through the rotor 22 and disperser 23 assemblies, depending onthe size and rotational speed of the rotor 22. A hollow draft tube 36can provide a lifting action for the liquid 18 at the bottom of thevessel 12 ensuring entire liquid capacity is traveling towards the rotor22. Inclusion of the water draft tube 36 facilitates capacity variationswithin the same geometry because all water that enters the rotorassembly is directed to the rotor suction from the bottom of vessel 12,reducing fluid bypass and short circuiting of the fluid around theturbulent areas. A single or multiple short baffles 38 might beinstalled at the bottom of the vessel 12 to prevent short circuiting ofthe contaminated liquid 18.

One or more collection reservoirs for contaminants can be provided. Inone non-restrictive embodiment, the contaminant reservoir 40 can beinstalled at the top of the inlet and outlet partition 34, 44 at eachend of the vessel 12. In another embodiment, a contaminant reservoir orskim collection channel 42 can be located at or near the center of thevessel 12 where the liquid surface 28 motion due to oil platform'smovement is at minimum. Skim collection channel 42 may at leastpartially surround the mechanism 22 for ingesting and mixing gas thatcreates a turbulent area in liquid 18, and which attracts the suspendedmatter or floc and carries it to the upper portion of vessel 12. “Atleast partially surround” is defined to mean a single channel thatcovers at least two sides of the mechanism 22. Skim collection channel42 may be substantially annular or circular or semi-circular, or atleast a closed loop or closed circuit, and may or may not be concentricwith the depurator or mechanism 22. By “substantially annular” is meantroughly circular and includes oval shapes. The skim collection channel42 may also substantially completely surround mechanism 22, by which ismeant surround at least 2700 of the circumference around mechanism 22.The advantage of this embodiment is to minimize the volume ofcontaminated liquid being skimmed off from the interface 28 and drainthrough opening 46. Minimizing skim volume is very important as itreduces treatment capacity and thereby the size of downstreamfacilities.

Skim collection channel 42 may be vertically adjustable to meet with theliquid level or interface 28, and/or alternatively, the liquid level orinterface 28 may be adjustable or regulated to meet with the skimcollection channel 42. These heights may be regulated by a controlmechanism, such as a programmable logic controller (PLC, not shown)which may work in conjunction with one or more level transmitters andone or more level control valves (not shown). Further details on inducedstatic flotation (ISF) collection channels may be seen in U.S. Pat. No.4,782,789, incorporated by reference herein. Convergence baffles 48 actas guides to direct or herd the froth towards the collection reservoirs40, 42.

The liquid 18 leaves the gasification chamber 30 passing underneath thepartition 50 through the channel 52 in an upward direction and over thepartition 44 into the capacity or outlet chamber 54 and out from outlet16. In one embodiment, partition 50 may be identical to partition 34 oralso be provided with a capacity to collect contaminants in the form offroth similar to contaminant reservoir 40. The upward motion of theliquid prior to its entrance into the outlet chamber 54, is of advantageto this invention, as upward movement of the liquid carries finercontaminants or any gas bubbles 20 escaping from the gasificationchamber 30 to the liquid interface 28, providing additional contaminantcleansing action prior to discharge.

In another non-limiting embodiment, the inventive apparatus or system 60may include a vertical cylinder vessel 62 with rotor assembly 22installed on the top thereof as shown in FIG. 2. Like reference numeralsare used to refer to like elements. By “vertically oriented” is meantthat the axis of the cylindrical vessel 62 is perpendicular or normal tothe ground or the oil recovery platform on which it is mounted. Thecontaminated liquid 18 enters the capacity or gasification chamber 64through at least one inlet opening 14. In this embodiment, the entirecapacity of the apparatus may be utilized for gasification or as agasification chamber 64. In one embodiment, the inlet opening 14 can beplaced tangential to the periphery of the vessel 62, in such way thatthe inlet velocity creates a moderate rotation in the liquid body insidethe vessel 62. When the direction of this rotation is in alignment withthe direction of rotor 22 rotation, the induced centrifugal movementcauses contaminants of larger specific gravity differential to bedisplaced towards the center of the vessel 62. This effect provides amoderate horizontal sweep in addition to vertical sweep as described inthe description of prior embodiment. The vertical sweep previouslydescribed applies to this embodiment as well. This additional sweep inone occasion can be utilized to minimize the residence time in thegasification chamber 64 by reducing the volume, without significantreduction in contaminant removal efficiency hence, resulting in smallerfootprint. In another occasion, this additional sweep can be utilized toimprove the contaminant removal efficiency for the same gasificationcapacity. The froth forms at the liquid interface 28 and is removedthrough skim collection channel 42 and opening 46. In anotherembodiment, a second, at least partially surrounding skim collectionchannel 66 can be located off-center and made by partition 67. Again, ahollow tube 36 can be utilized to lift the liquid from the bottom of thevessel 62 towards the rotor 22 to ensure multiple passes ofgasification. Series of baffles 68 and 69 can be utilized to control orenhance the hydrodynamics within the gasification chamber 64. The gasremains in circulation throughout the gasification chamber 64 and is notconsumed. In one embodiment of the invention, the vapor space in theupper portion of vessels 12 and 62 is sealed off, that is, it is notopen to the atmosphere.

Another innovation herein pertains to the method of froth collection. Insome prior apparatus, the froth is removed by means of partitioning asmall length of the tank or vessel on each end of the gasificationchamber or between the two consecutive chambers. In contrast, includedherein is a new design for the froth collection reservoir or channel.Shown in FIGS. 3A and 3B is one non-limiting embodiment of such designwhich demonstrates a collection channel 70 located peripherally or nearto a stand pipe 72, creating an enclosed capacity or reservoir 74between two concentric partitions, inner partition 76 and outerpartition 78. The outer and inner rims 76 and 78 of the reservoir may beequipped with plurality of v-notches or other shape contours 80 throughwhich the suspended matter or contaminants pass. Convergence baffles 82and 84 may be provided and installed at an angle on the outer peripheryor in some other fashion to the vessel 12/62 or vessel internals, toguide the froth towards the collection channel 70 by harnessing therotational motion of the fluid, exerted by the rotor 22. The collectedfroth then, is routed into the drain 46 or plurality thereof, and leavesthrough the vessel wall (not shown in FIG. 3).

FIGS. 4A, 4B, and 4C present another non-restrictive embodiment of thefroth collection channel 70′, which includes either a cylindrical (FIG.4C) or frustoconical (FIG. 4B) partition 78′ on the outside and thestandpipe 72′ on the inside, creating the capacity 74′. The periphery ofthe outer rim 78′ can be equipped with plurality of v-notches or othershape contours 80′. Similarly, convergence baffles 82 and 84 can beprovided as guides for the froth to the collection reservoir or channel70′. Froth then leaves the tank through opening or drain 46.

Another important feature of the invention is intermittent skimming ofthe suspended matter by raising the skim level (e.g. froth level orfluid level 28) in order to remove the suspended matter or skim oil forhigh pitch and roll conditions on a floating production platform. Itwill be appreciated that on a floating offshore hydrocarbon recoveryplatform (or any other environment subject to excessive motion) it ispossible for excessive wave action, such as during storms, hurricanesand other conditions that the platform may pitch and/or rollexcessively. By “excessively” is meant to the detriment of the presentmethod of clarifying water. That is, during consequent pitching and/orrolling of system 10/60, some clarified water would be undesirablycollected by skim channel 42 caused by froth levels or fluid levels 28splashing over or sloshing over excessively into these channels.

This waste of clarified water may be minimized by controlling frothlevel or fluid level 28. The control of the height of this level may bethrough a PLC via a level control valve (LCV, not shown) in response topitch and/or roll data collected by pitch and roll sensor (not shown).It will be appreciated that the exact nature of pitch and roll sensor isnot critical and may be achieved by various angle or pitch sensorsconventionally available. It is not necessary that the pitch and rollsensor be a single device, but may be two or more devices.

An optional chemical feed unit (not shown), which is a standard feedunit for dispensing a metered amount of a flocculant chemical, using apolymer or a demulsifier, into fluid 18, to initially treat the influentfor achieving optimum separation of contaminants from the water can beprovided.

Although not shown, valves may be provided for blowdown of sludge thatcollects in the bottom of vessel 12. Also not shown are optional gaugesto monitor the pressure of the effluent and the flow of gas, and asystem for replacing or replenishing gas, as necessary.

In the method of the invention, using the FIG. 1 embodiment except asnoted, a continuous flow of liquid 18 having suspended matter mixedtherewith is introduced into inlet chamber 32 (if present, otherwise,directly into gasification chamber 64 in the FIG. 2 embodiment) throughinlet 14. Some separation of the suspended matter occurs in inletchamber 32 by floating to the upper portion of inlet chamber 32. Thisfroth or suspended matter is collected in containment reservoir 40 adrain opening (not shown, but similar to 46) to a consolidatingcollection channel away from vessel 12. As noted, in one embodiment ofthe invention, froth level 28 may be controlled. That is, during periodsof undesirable or detrimental pitch or roll, froth level 28 may belowered below skim collection chamber 42 and/or 40 then ramped up orintermittently raised during or for collection. Controls for changinglevel 28 are not shown, but would be known to those skilled in the art.

Fluid 18, still containing considerable suspended matter, underflowspartition 34 into gasification chamber 30 (gasification chamber 64 inFIG. 2) where a flow of gas is introduced into the liquid 18 by gasingesting and mixing mechanism 22, creating a turbulent area in theentirety of chambers 30 or 64, and allowing the gas to attract thesuspended matter and carry it to the upper portion of vessel 12 where itfloats at level 28. This suspended matter is collected in skimcollection channel 42 that at least partially surrounds the mixingmechanism 22 (and also reservoir 40 and channel 66, if present). Theskim collection channel 42 (and channel 66, if present) mayalternatively completely surround mixing mechanism 22, as in theembodiments shown in FIGS. 3 and 4. The suspended matter is deliveredthrough drain opening 46. At least one baffle 82 or 84 near the skimcollection channel 42 dampens the motion of the fluid 18 that occurswhen vessel is rocked or moved in response to waves hitting thehydrocarbon production platform.

Fluid 18, largely free of suspended matter, next underflows partition 50(or as in FIG. 2 directly exits vessel 12 through outlet 16) and flowsthrough channel 52 into outlet chamber 54. Passage of the fluid 18 fromoutlet chamber 54 through outlet 16 may optionally be regulated by alevel control valve (not shown) in response to signals from a PLC (notshown) according to a software program therein using information from alevel transmitter according to techniques and apparatus known to thoseskilled in the art.

To summarize, advantages of the invention include, but are notnecessarily limited to, a decreased “footprint” (decreased spacerequirements), reduced power requirements, reduced capital and operatingcosts, and improved tolerance to platform wave motion effects, ascompared with conventional mechanical flotation systems, such as four-or two-cell systems. These advantages are achieved through asingle-cell, mechanical, cylindrical gas flotation system with abaffling and floc collection design to minimize surface wave action.Level control in some embodiments will ensure proper rotor submergenceof the gas ingesting mechanism and provide a stable level at the frothsurface to allow controlled skimming and enhanced performance. Use ofdraft tubes in connection with the gas ingesting and mixing mechanismsminimize short-circuiting over a wide range of capacities.

Field tests and results of actual installations for two and fourgasification-cell self-induced gas floatation apparatus have proven highcontaminant removal efficiency with reduced footprint. Based on theseresults, the current invention is expected to provide similarperformance up to 85% or better removal of suspended matter, withsignificant economical advantages including, but not necessarily limitedto, the apparatus footprint, power consumption and most importantlyflotation gas consumption.

In the present invention, using only one gasification chamber or celland a residence time in each chamber of about 2.0 to 2.5 minutes, theefficiency achieved of about 70-75% or more is comparable to thatobtained using a dual-cell design, but at much less power utilizationthan other single cell systems. That is, with the inventive apparatus,while efficiency is slightly reduced, the horsepower requirements aremuch less that of a conventional system (since only one gasingesting/mixing mechanism is required instead of two or four), and the“footprint” or area consumed by the apparatus is reduced by nearlyhalf—an important consideration on an offshore oil platform where spaceis at a premium.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof, and has been demonstrated aseffective in providing a mechanical flotation system for removingsuspended matter from liquids. However, it will be evident that variousmodifications and changes can be made thereto without departing from thebroader spirit or scope of the invention as set forth in the appendedclaims. Accordingly, the specification is to be regarded in anillustrative rather than a restrictive sense. For example, the distancesbetween the partitions and the volumes of the various chambers may bechanged or optimized from that illustrated and described, and eventhough they were not specifically identified or tried in a particularapparatus, would be anticipated to be within the scope of thisinvention. Similarly, gas ingestion and mixing mechanisms, and leveltransmitting and control devices different from those illustrated anddescribed herein would be expected to find utility and be encompassed bythe appended claims. Further, liquid level control and skimming andcollecting patterns or protocols different from those explicitlydescribed here may nevertheless fall within the scope of the invention.

1. An apparatus for removing suspended matter from a liquid, comprising:a) a vessel for receiving a flow of liquid having suspended mattertherein; b) an inlet to introduce the flow of liquid into the vessel; c)an outlet for removing clarified liquid from the vessel; d) a gas layerin the upper portion of the vessel; e) a mechanism in the vessel foringesting and mixing gas into the liquid for creating a turbulent areaand for attracting the suspended matter and for carrying the suspendedmatter to an upper portion of the vessel, the interface of the gas layerand liquid being a liquid level; f) a skim collection channel at leastpartially surrounding the mechanism for collecting suspended matter inthe upper portion of the vessel and removing the suspended matter by adrain.
 2. The apparatus of claim 1 where the gas layer is not open tothe atmosphere.
 3. The apparatus of claim 1 where the skim collectionchannel is substantially annular and substantially completely surroundsthe mechanism.
 4. The apparatus of claim 3 where the skim collectionchannel is circular and concentric with the mechanism.
 5. The apparatusof claim 1 further comprising: g) at least one baffle near the skimcollection channel to direct the suspended matter to the skim collectionchannel.
 6. The apparatus of claim 1 where the vessel is a cylindricalpressure vessel oriented vertically.
 7. The apparatus of claim 6 wherethe vessel has a periphery and the inlet is angled tangentially to theperiphery to create liquid rotation inside the vessel.
 8. The apparatusof claim 1 where the vessel is a cylindrical pressure vessel orientedhorizontally, and the vessel further comprises an inlet chamber, onegasification chamber and an outlet chamber, where the inlet chamber isbetween the inlet and the gasification chamber and where the outletchamber is between the gasification chamber and the outlet, and theinlet chamber, gasification chamber and outlet chamber are divided bypartitions and the liquid flows between chambers under the partitions.9. An apparatus for removing suspended matter from a liquid, comprising:a) a vessel for receiving a flow of liquid having suspended mattertherein; b) a plurality of partitions sequentially dividing the vesselinto an inlet chamber, a single gasification chamber, and an outletchamber, each adjacent chamber fluidly communicating with one another;c) an inlet to introduce the flow of liquid into the inlet chamber; d)an outlet for removing clarified liquid from the outlet chamber; e) agas layer in the upper portion of the vessel; f) a mechanism forIngesting and mixing gas into the liquid of the gasification chamber forcreating a turbulent area and for attracting the suspended matter andfor carrying the suspended matter to an upper portion of the vessel, theinterface of the gas and liquid being a liquid level; and g) a skimcollection channel at least partially surrounding the mechanism forcollecting suspended matter in the upper portion of the vessel andremoving the suspended matter by a drain.
 10. The apparatus of claim 9where the gas layer is not open to the atmosphere.
 11. The apparatus ofclaim 9 where the skim collection channel is substantially annular andsubstantially completely surrounds the mechanism.
 12. The apparatus ofclaim 11 where the skim collection channel is circular and concentricwith the mechanism.
 13. The apparatus of claim 9 further comprising: h)at least one baffle near the skim collection channel to direct thesuspended matter to the skim collection channel.
 14. The apparatus ofclaim 9 where the vessel is a cylindrical pressure vessel orientedhorizontally.
 15. A method for clarifying liquid from suspended matter,the method comprising: a) providing a vessel; b) introducing a flow ofliquid having suspended matter into the vessel through an inlet; c)providing a gas layer in the upper portion of the vessel, whereinterface of the gas layer and liquid is a liquid level; d) ingestingand mixing gas into the liquid of the vessel by creating a turbulentarea and for attracting the suspended matter and for carrying thesuspended matter to an upper portion of the vessel at the liquid levelusing a mechanism; e) collecting suspended matter in a skim collectionchannel that at least partially surrounds the mechanism; and f) removingclarified liquid through an outlet.
 16. The method of claim 15 furthercomprising controlling the liquid level in the vessel by regulating flowthrough a valve in the outlet.
 17. The method of claim 15 furthercomprising controlling the liquid level in response to the movement ofthe vessel.
 18. The method of claim 15 further comprising controllingthe liquid level in response to the pitch or roll of the vessel.
 19. Themethod of claim 15 where the gas layer is not open to the atmosphere.20. The method of claim 15 where the skim collection channel issubstantially annular and substantially completely surrounds themechanism.
 21. The method of claim 20 where the skim collection channelis circular and concentric with the mechanism.
 22. The method of claim15 where the vessel further comprises at least one baffle near the skimcollection channel to direct the suspended matter to the skim collectionchannel.
 23. The method of claim 15 where the vessel is a cylindricalpressure vessel oriented vertically.
 24. The method of claim 23 wherethe vessel has a periphery and the inlet is angled tangentially to theperiphery and the method further comprises creating liquid rotationinside the vessel when liquid is introduced into the vessel.
 25. Themethod of claim 15 where the vessel is a cylindrical pressure vesseloriented horizontally.
 26. The method of claim 15 where the clarifyingis conducted under pressure.